Data_Sheet_2_Antimicrobial Activity and Identification of the Biosynthetic Gene Cluster of X-14952B From Streptomyces sp. 135.ZIP

The bacterial genus Streptomyces is an important source of antibiotics, and genome mining is a valuable tool to explore the potential of microbial biosynthesis in members of this genus. This study reports an actinomycete strain 135, which was isolated from Qinghai-Tibet Plateau in China and displayed broad antimicrobial activity. The fermentation broth of strain 135 displayed strong antifungal activity (>70%) against Sclerotinia sclerotiorum, Botrytis cinerea, Valsa mali, Phytophthora capsici, Glomerella cingulata, Magnaporthe grisea, Bipolaris maydis, Exserohilum turcicum in vitro, meanwhile possessed significant preventive and curative efficacy against S. sclerotiorum, Gaeumannomyces graminis, and P. capsici on rape leaves (54.04 and 74.18%), wheat (90.66 and 67.99%), and pepper plants (79.33 and 66.67%). X-14952B showed the greatest antifungal activity against S. sclerotiorum and Fusarium graminearum which the 50% inhibition concentration (EC50) were up to 0.049 and 0.04 μg/mL, respectively. Characterization of strain 135 using a polyphasic approach revealed that the strain displayed typical features of the genus Streptomyces. 16S rRNA gene sequencing and phylogenetic analysis demonstrated that the isolate was most closely related to and formed a clade with Streptomyces huasconensis HST28T (98.96% 16S rRNA gene sequence similarity). Average nucleotide identity (ANI) and DNA-DNA hybridization (DDH) values in strain 135 and related type strains were both below the threshold of species determination (91.39 and 56.5%, respectively). OrthoANI values between strain 135 and related type strains are under the cutoff of determining species (<95%). The biosynthetic gene cluster (BGC) designated to X-14952B biosynthesis was identified through genome mining and the possible biosynthesis process was deduced.

链霉菌属（Streptomyces）是一类重要的抗生素来源，而基因组挖掘（genome mining）是探索该属微生物生物合成潜力的宝贵工具。本研究报道了一株分离自中国青藏高原的放线菌菌株135，其展现出广谱抗菌活性。该菌株135的发酵液在体外对核盘菌（Sclerotinia sclerotiorum）、灰葡萄孢（Botrytis cinerea）、苹果腐烂病菌（Valsa mali）、辣椒疫霉（Phytophthora capsici）、围小丛壳（Glomerella cingulata）、稻瘟病菌（Magnaporthe grisea）、玉米小斑病菌（Bipolaris maydis）以及玉米大斑病菌（Exserohilum turcicum）均表现出较强的抗真菌活性（抑制率>70%）；同时其对油菜叶片上的核盘菌、全蚀病菌（Gaeumannomyces graminis）以及辣椒植株上的辣椒疫霉分别展现出显著的预防与治疗效果，对应预防与治疗效率分别为54.04%与74.18%、小麦上为90.66%与67.99%、辣椒植株上为79.33%与66.67%。化合物X-14952B对核盘菌与禾谷镰孢菌（Fusarium graminearum）的抗真菌活性最强，其半数抑制浓度（EC50）分别可达0.049 μg/mL与0.04 μg/mL。通过多相分类法对菌株135进行鉴定，结果显示该菌株具备链霉菌属的典型特征。16S rRNA基因测序与系统发育分析表明，该分离株与华顺链霉菌（Streptomyces huasconensis）HST28T的亲缘关系最近，二者16S rRNA基因序列相似度达98.96%，并形成了一个单源进化支。菌株135与相关模式菌株的平均核苷酸同源性（ANI）以及DNA-DNA杂交（DDH）值均低于物种界定阈值（分别为91.39%与56.5%）；菌株135与相关模式菌株的正交平均核苷酸同源性（OrthoANI）也低于物种判定临界值（<95%）。本研究通过基因组挖掘鉴定出了负责X-14952B生物合成的生物合成基因簇（BGC），并推导了其可能的生物合成途径。